The present invention relates to the field of hose fittings and, in particular, to a reusable fitting for use in fluid conveying lines.
Hose fittings are universally used for connecting the ends of fluid conveying lines to their associated accessories for fluid delivery, control or operation in pneumatic and/or liquid applications and under widely varying chemical environments. Such fittings fall into two general categories, original equipment fittings and reusable fittings. In the former category, the hose, together with the fittings, is assembled as a unit by the manufacturer. Because of the product volume associated therewith, sophisticated and expensive tooling may be used to provide economical manufacturing costs. Through automated stripping and crimping operations, the fitting is integrally assembled to a precut length of tubing to form an assembled unit. Such hose assemblies however, are expensive to maintain in service. Should any of the fluid line components fail, the entire hose line must be replaced, even though only one of the components may be non-functional. Because of the production techniques, the other parts cannot be salvaged and reused. In order to maintain production, a large inventory of such assemblies must be carried by the user to minimize the equipment downtime. These problems have been significantly overcome through the adoption of reusable fittings. Upon failure of the original equipment, a new hose assembly is constructed from hose cut to length from a bulk inventory of hose. Reusable fittings are connected to the ends of the hose line to form the replacement assembly. Thereafter, should any of the components fail in service, only the defective part needs to be replaced. Inasmuch as the predominant failure is at the hose, the reusable fittings constitute an in-service inventory of parts such that only the replacement hose must be carried in inventory leading the economical purchase of bulk hose cut to length on an as-required basis. The fittings are salvaged and reused in the replacement assembly. Significant savings thus result, often up to 70% of the cost of the pre-assembly hose lines. Thus, reusable fittings secure a significant market penetration.
Reusable fittings, however, also have constraints in competing with high quality assembled units. They must provide similar performance thus requiring precision machining and accurate assembly. They also must be readily disassembled, without sacrifice of the fitting, and reassembled with a minimum of equipment shutdown.
Replacement hose lines requir removal of the entire line from the accessories for disassembly of the fittings and the hose. In a conventional reusable fitting, reassembly requires cutting a replacement hose to the desired length and preparing the hose ends by stripping or skivving the outer covering. The fitting includes an external socket which is clamped in a vise and the skived hose end is inserted into one end thereof. A nipple is then screwed into the other end of the socket and the hose to complete the assembly. To avoid distorting the nipple during assembly, a mandrel is oftentimes required. Because the fittings are integral with the hose, adapter fittings are required to avoid twisting of the hose during connection to the accessories to thereby prevent separation of the wall plies with a consequent loss of strength. The requirements of complete disassembly of the fittings for repair, the special tools and need for adaptive connectors increase the time and cost of repair.
Segmented reusable fittings have been used for inline flanged couplings using large diameter, substantially high pressure hoses. Such segmented reusable fittings have advantages in that they reduce end preparation and provide high compressive loadings at the nipple hose interface. However, they are disadvantageous in that complete removal is required for repair. Moreover, the segments must be accurately circumferentially aligned to provide uniform compression of the hose and to prevent distortion of the nipple. This can only be achieved by vertical assembly. Thereafter, by means of an expensive assembly tool, the segments are compressed and a retaining band inserted over the compressed segment and the assembly tool removed. It has been proposed in U.S. Pat. No. 2,880,020 to use wedge-shaped segments and the coupling flange to generate the compressive force on the segments thereby reducing the need for the need for complex assembly tools. However, such a coupling also requires complete disassembly from the line, vertical and manual orientation of the segments and a supplemental drawing plate and bolts which are tightened to slide the flange over the segments to the assembled position. The flange and draw bolts removed and the fitting and hose sub-assembly are then coupled in line at a mating flange.